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Do Now: (5 min)

Do Now: (5 min). Explain why atoms are neutral in charge. When you are finished, bring it up to the front within the first 5 minutes of class to get credit for your work!. Do Now Discussion. Why are atoms neutral in charge? Protons and electrons have opposite charges

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Do Now: (5 min)

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  1. Do Now: (5 min) Explain why atoms are neutral in charge. When you are finished, bring it up to the front within the first 5 minutes of class to get credit for your work!

  2. Do Now Discussion Why are atoms neutral in charge? • Protons and electrons have opposite charges • Atoms have the same number of protons and electrons • The charges cancel each other out!

  3. Atomic Structure: Mass Number 10/22/09 HAPPY THURSDAY! Agenda: • Cornell Notes (short!!) • Tic-Tac-Toe Practice • Atom Brochures (if we work quickly)

  4. What we’ve learned • 3 subatomic particles • Proton • Neutron • Electron • Atoms are neutral because # protons = # electrons • Atomic number = # of protons which determines the type of element

  5. Mass Number The number of protons and neutrons in an atom Mass number = protons + neutrons -or- protons = mass number - neutrons -or- neutrons = mass number - protons

  6. Examples: Calculating Mass Number • If an atom has 8 protons and 4 neutrons, what is the mass number? Mass number = protons + neutrons = 8 + 4 = 12 • If an atom has 7 protons as 15 neutrons, what is the mass number? Mass number = 7 + 15 = 22

  7. Examples: Calculating the Number of Protons • If an atom has a mass number of 20 and has 14 neutrons, how many protons does it have? Protons = mass number – neutrons = 20 – 14 = 6 protons! • If an atom has a mass number of 45 and has 15 neutrons, how many protons does it have? Protons = 45 – 15 = 30 protons!

  8. Examples: Calculating the Number of Neutrons • An atom has a mass number of 12 and has 9 protons. How many neutrons does it have? neutrons = mass number – protons = 12 – 9 = 3 neutrons! • If an atom has 31 protons and a mass number of 56, how many neutrons does it have? neutrons = 56 – 31 = 25 neutrons!

  9. Calculating the number of charged particles in an atom/compound # charged particles = protons + electrons Example Problem: • A lithium atom (Li) has how many charged particles? Atomic Number = 3 3 protons + 3 electrons = 6 charged particles!

  10. Examples: Calculating the number of charged particles • A potassium (K) has an atomic number of 19. How many charged particles does it have? charged particles = electrons + protons = 19 + 19 = 38 charged particles! • One formula unit of KF has how many charged particles? K has 19 + 19 = 38 charged particles F has 9 + 9 = 18 charged particles KF has 38 + 18 = 56 charged particles!

  11. Tic-Tac-Toe Practice • There are 9 practice activities to choose from • You will choose and complete one activity at a time from the board • You will complete the activity in the designated box on your board (i.e. answers for activity 1 go in box 1) • Make sure you show all your work! • When you are finished with an activity, have Ms. Akagi check it off and return the card to the board. • The Mission: complete three activities so that you get a Tic-Tac-Toe! (3 in a row) • You will be turning in your work at the end of class! • When finished, you can use the rest of the time to finish your atom brochure (we will also have some time next week)

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